So, what's the verdict on Scorpion cat back mufflers for the m20? They're on sale right now from Bavauto and I'm thinking about getting one even though I really want something like a Stromung, which are like twice as much money. I want it to last for a long time and not be much louder than stock. I've listened to some sound clips and it doesn't sound to shabby, but i'm more interested in knowing how they hold up over time and what the build quality is like.